Method of producing surfacing material



Patented Oct. 6, 1936 UNITED STATES PATENT OFFICE MAT ERIAL Willie L. Holbrook and William R. Parker, Houston, Tex.

No Drawing. Application January 12, 1935, Serial No. 1,544

3 Claims.

This invention relates to a method of producing a surfacing material and has for its object the production of material particularly adapted for use in constructing paving, sidewalks, floors, and similar purposes requiring a hard surface.

The invention comprehends a novel method of combining shell and asphalt, or other suitable bitumen; and also involves the use of steam, either wet or dry, for heating the shell to facilitate coating of the shell with the bitumen.

In carrying out the process, the shell, such as oyster or clam shell, should be washed and graded and should comprise the required relative amounts of coarse, fine, and medium shell, and in some cases, it may be found desirable to add a filler in order to fill the voids.

The asphalt or bitumen used may be either ordinary asphalt or an asphalt cut back with a solvent such as, for example, naphtha, the character of the asphalt depending on the desired penetration or the nature of the shell.

The cleansed and graded shell should be agitated in a suitable mixer and during the mixing or agitating of the shell, fine grindings will be produced. The shell is subjected to hot steam during the agitating or mixing process, and the bitumen is sprayed over the mass of shell. The shell being harder and tougher than the asphalt, grinds the asphalt and forms it into very small globules, and the dispersion agent which is formed by the grinding of the shell against each other in the process of heating and mixing, is of the nature of a lime paste, and this paste, which is the product of the shell grindings and the moisture contained in the shell, causes an emulsification of the asphalt. In case the shell does not contain the required amount of moisture to bring about this emulsification, a suflicient amount of heated water may be added during the heating process, or if the asphalt is of such a nature as not to mix readily, the required amount of. solvent may be added during the process, or before.

The asphalt should be heated to a temperature that will cause it to thoroughly mix with the shell and to become emulsified during the grinding process while being mixed with the shell. The degree of heat to which the shell should be subjected will depend largely upon the quality of the asphalt used.

The steam should be applied to the shell while the shell is being agitated so as to bring the shell to a uniform temperature before the asphalt is sprayed on to the shell in the mixer. The fine grindings from the shell form a paste of calcium carbonate that holds the asphalt in temporary suspension after it has been ground into small particles with the mixture and calcium carbonate paste, by the shell, while they are being agitated, and this keeps the mixture from hardening until the material has been laid on the roadway or other location and the moisture. has evaporated.

When the mixing process has been completed, the shell is completely coated with the asphalt and its moisture is retained, and it will be sealed off from the absorption of outside moisture. After enough moisture has evaporated, the small globules or particles of asphalt will reunite after the mixture has been laid for its intended use, and the material will start to set up and harden. After being laid to the desired thickness, the mixture should be rolled and/or camped in order to knead all of the shellinto their proper places so as to leave the surface smooth, but if desired, the mixture may be laid in layers and each layer rolled and tamped before the next succeeding layer is put down.

What we claim is:-

1. The process of producing a surfacing material which consists of agitating a mass of moist shell and subjecting the mass to heated steam and a bitumen while being agitated, then allowing the material to set. 2. The process of producing a surfacing material which comprises agitating a mass of shell, applying moisture and hot steam thereto, then adding a bitumen, such as asphalt, to the heated shell and continuing the mixing operation until the shell and bitumen are thoroughly mingled together.

3. The process of producing a surfacing material which comprises agitating a mass of shell, applying hot steam and water thereto, spraying a bitumen over the mass of shell, continuing the agitation to cause the production of shell dust by grinding the shell against each other and to form the bitumen into small globules and to mix said dust, bitumen and the moisture to form an emulsified paste around the individual shell forming a seal to exclude the absorption of moisture.

WILLIE L. HOLBROOK. WILLIAM R. PARKER. 

